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January 10th-12th OV/MW/GL Winter Storm prospects

Harry

By Harry,
in Central/Western States

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Stebo

Stebo

Posted
Posted
SOME LIGHT SNOW MAY MOVE INTO THE SW CORNER OF THE CWA BY LATE

MONDAY NIGHT SO HAVE ADDED POPS THERE. THIS SYSTEM HAS BEEN LOOKING

SOMEWHAT STRONGER ON THE PAST FEW MODEL RUNS AND SHOULD BRING US

SOME ACCUMULATING SNOWS INTO TUESDAY. THE UPPER LOW OVER MT THIS

MORNING WILL MERGE WITH THE SOUTHERN STREAM ENERGY OVER TX AND FORM

A SURFACE LOW PRESSURE THAT IS EXPECTED TO MOVE NE ACROSS OH ON

TUESDAY. MID LEVEL FGEN FORCING IS INDICATED OVER FAR SOUTHERN

LOWER COMBINED WITH WEAK NEGATIVE EPV ABOVE THE FGEN. THIS COULD

RESULT IN HIGHER THAN EXPECTED AMOUNTS OF SNOWFALL AS SMALL SCALE

HEAVIER SNOW BANDS COULD FORM. FOR NOW HAVE INCREASED POPS TO

LIKELY ACROSS THE CWA BY TUESDAY AFTERNOON. ACCUMS SHOULD BE IN THE

2-4 INCH RANGE OVER THE SOUTHERN CWA...WITH LESSER AMOUNTS NORTH OF

I-96. BUT WE WILL HAVE TO CONTINUE TO MONITOR HOW THE FGEN MAY COME

INTO PLAY AS THIS SYSTEM APPROACHES.

per GRR

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Thundersnow12

Thundersnow12

Posted
Posted

6z NAM is dropping more snow here then the 0z run..

and from LOT's AFD..

ATTENTION WILL TURN TO THE WEST AS VIGOROUS UPPER LEVEL TROUGH

EJECTS OUT OVER THE COLORADO ROCKIES MONDAY AND APPROACHES THE

MID-MISSISSIPPI RIVER VALLEY MONDAY NIGHT INTO TUESDAY. MODELS HAVE

BEEN FAIRLY CONSISTENT RUN-TO-RUN IN KEEPING SURFACE CYCLONE WELL

SOUTH OF THE FORECAST AREA...TRACKING JUST SOUTH OF THE OHIO RIVER

VALLEY. WHILE BEST FORCING WILL REMAIN SOUTH OF THE FORECAST

AREA...PROLONGED PERIOD OF UPWARD VERTICAL VELOCITIES FROM OVER

NORTHERN ILLINOIS AND NORTHWEST INDIANA WILL ALLOW AIR COLUMN TO

SATURATE. IN ADDITION...A FAIRLY DEEP 8K FT DENDRITIC GROWTH ZONE

WILL ALLOW FOR BIG FLAKES TO DEVELOP. GFS COBB OUTPUT SUGGESTS

15-16:1 SNOW TO LIQUID RATIOS...WHILE NAM SUGGESTS EVEN HIGHER

RATIOS /20-21:1 AT TIMES/ WITH SIMILAR QFP AMOUNTS AS THE GFS. THIS

EVENT IS SHAPING UP TO BE SUB-ADVISORY CRITERIA...BUT COULD SEE A

GOOD 18 HOURS OR SO OF LIGHTLY ACCUMULATING SNOWFALL.

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Thundersnow12

Thundersnow12

Posted
Posted

DVN

MAIN FOCUS IS WITH SNOW EVENT MON-TUE. MODELS IN GOOD AGREEMENT

DEPICTING UPPER LOW OVER MT GRADUALLY SHIFTING E/SE INTO THE

PLAINS MON-TUE... WITH SHORTWAVE ENERGY EJECTING IN SOMEWHAT

OF NEGATIVE TILT FROM BASE OF TROUGH EWD FROM ROCKIES INTO THE

OH VLY. SNOW IN THE PLAINS ATTENDANT TO STRONG UPPER DIVERGENCE

AND SFC-850 MB INVERTED TROUGH... WILL SPREAD EWD IN TIME.

DRY EASTERLY LLVL FLOW WILL INHIBIT EWD PROGRESSION SOME ON

MON WITH BEST CHCS FOR -SN ARRIVING MON AFTN ACROSS THE WEST

AND SOUTHWEST CWA. SNOW WILL CONTINUE OVERSPREADING REST OF THE

CWA MON EVE AND CONTINUE THROUGH TUE. TSECTS SHOW BULK OF LIFT

OUTSIDE OF FAVORABLE DENDRITIC GROWTH ZONE... SO ANTICIPATE

MAINLY A LONG DURATION (18-24 HRS) LIGHT SNOW. THAT BEING

SAID... THERE IS LIKELY TO BE A PERIOD OF MODERATE SNOW FOR A TIME

MON EVE THROUGH ABOUT DAYBREAK ON TUE WHEN STRONGER FORCING

ARRIVES... FOCUSED MAINLY ACROSS THE SOUTHWEST 1/3-1/2 OF CWA BASED

ON TRACKS OF 850 MB AND 700 MB LOWS. A BIT CONCERNING TO SEE

00Z NAM BUFKIT SOUNDING DEPICTING SUCH A DEEP DENDRITIC GROWTH ZONE

OF 150 TO NEARLY 200 MB IN ROUGHLY 06Z-12Z... WHICH IN CONCERT

WITH ARRIVAL OF MAIN FORCING. THUS... POTENTIAL TO SEE HIGHER SNOW

TO WATER RATIOS AND AS RESULT SNOW COULD ADD UP QUICKLY. DONT

SEE QPF MORE THAN 0.25 INCH IN 12 HR PERIOD FROM 00Z MON-12Z TUE

THUS EVEN IF AS HIGH AS 20:1 RATIOS WOULD BE TALKING ABOUT

5 INCHES IN 12 HR PD... BELOW WARNING CRITERIA OF 6 IN/12 HR.

AND... PROBS WHILE NOT ZERO ARE AWFULLY LOW TO OTHER WARNING

CRITERIA OF 8 IN/24 HRS. BUT... THIS WINTER HAS SHOWN EACH SYSTEM

TO BRING RELATIVELY NARROW SWATHS OF WARNING CRITERIA SNOWS... SO

HAVE TO KEEP EYE ON. VARIOUS TECHNIQUES INCLUDING GARCIA METHOD

ADJUSTED FOR LONG DURATION OF MAINLY LIGHTER FORCING SUPPORTS MAX

AMOUNTS OF 5-6" OVER THE 18-24 HRS... WITH THESE HIGHER ACCUMS

POTENTIAL SUGGESTED SOUTHWEST OF KCID-KGBG LINE ATTIM... OTHERWISE

GENERAL 2-4" AMOUNTS OF CWA. GRADIENT SHOWING A BIT MORE OF AN

INCREASE ON TNGT MODEL RUNS AND SO 10-20 MPH WINDS POSSIBLE BY

TUE AFTN INTO EVE WHICH COULD BRING ABOUT POCKETS OF SOME BLOWING

AND DRIFTING. BARRING ANY SIGNIFICANT MODEL CHANGES WE ARE PROBABLY

HEADED TOWARD AN ADVISORY FOR PORTIONS OF THE AREA... ESPECIALLY SW

1/3-1/2 AS SUGGESTED ATTIM.

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Baum

Baum

Posted
Posted

". WHILE BEST FORCING WILL REMAIN SOUTH OF THE FORECAST

AREA...PROLONGED PERIOD OF UPWARD VERTICAL VELOCITIES FROM OVER

NORTHERN ILLINOIS AND NORTHWEST INDIANA WILL ALLOW AIR COLUMN TO

SATURATE. IN ADDITION...A FAIRLY DEEP 8K FT DENDRITIC GROWTH ZONE

WILL ALLOW FOR BIG FLAKES TO DEVELOP. GFS COBB OUTPUT SUGGESTS

15-16:1 SNOW TO LIQUID RATIOS...WHILE NAM SUGGESTS EVEN HIGHER

RATIOS /20-21:1 AT TIMES/ WITH SIMILAR QFP AMOUNTS AS THE GFS. THIS

EVENT IS SHAPING UP TO BE SUB-ADVISORY CRITERIA...BUT COULD SEE A

GOOD 18 HOURS OR SO OF LIGHTLY ACCUMULATING SNOWFALL. "....:blahblah:

unless you see Aleking on this board no reason to get excited....this could turn out to be Chicago areas storm of the year..for the rest of the year. As has been the case all winter areas west and south may cash in big on great ratios while dry air chews up our area.:yikes:

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michsnowfreak

michsnowfreak

Posted
Posted

DTX updated, being conservative as of right now, but mentioned the chance of snowfall accums going up.. They are forecasting 1-3" of snowfall right now, I think those number could double if everything plays out.

http://forecast.weat...on=1&glossary=1

UPPER LEVEL SHORTWAVE RIDGE BUILDS OVERHEAD ON MONDAY AS THE WESTERN

TROUGH ADVANCES INTO THE PLAINS. IN TYPICAL FASHION...THE MODELS ARE

NOW STRONGER WITH THE JET ENERGY MOVING ONTO THE WEST COAST WHICH

WILL ROUND THE TROUGH AND SLIDE THROUGH THE OHIO/TENNESSEE VALLEYS

INTO TUESDAY. THE 00Z MODELS HAVE TRENDED TOWARDS A MORE PHASED AND

COMPACT UPPER LEVEL WAVE LIFTING THROUGH THE UPPER OHIO VALLEY ON

TUESDAY WHICH EVEN CLOSES OFF IN THE CLEVELAND VICINITY BY 06Z

WEDNESDAY. THIS FAVORS A MORE NORTHWESTWARD TRACK FOR THE WEAK

SURFACE LOW THAT DEVELOPS IN THE TENNESSEE VALLEY AND TRACKS UP

THE WEST SIDE OF THE APPALACHIANS. WITH NEARLY ALL OF THE 00Z MODELS

PICKING UP ON THIS TREND...SOME ADJUSTMENTS HAVE BEEN MADE TO THE

TUESDAY FORECAST. ISENTROPIC ASCENT WILL INCREASE IN THE 280-290K

LAYER ON TUESDAY WITH LIGHT TO MODERATE SNOW OVERSPREADING

SOUTHEAST MICHIGAN DURING THE AFTERNOON. SPECIFIC HUMIDITIES REACH

AS HIGH AS 2 G/KG NEAR THE OHIO BORDER...WHILE LOCATIONS TO THE

NORTH ARE CLOSER TO JUST 1 G/KG. SNOW IS EXPECTED TO CONTINUE INTO

THE EVENING HOURS AS DEFORMATION INCREASES ON THE NORTHWEST FLANK

OF THE DEEPENING UPPER LEVEL CIRCULATION. WITH MOISTURE LOOKING

LIKE A LIMITING FACTOR...HAVE MADE SOME CONSERVATIVE ADJUSTMENTS

TO THE FORECAST RAISING MOST AREAS TO 60 PERCENT POPS WITH 1-2.5

INCHES OF SNOW(HIGHEST IN THE SOUTH). IF MODELS CONTINUE TO SHOW A

DEEPENING TREND THEN SNOWFALL AMOUNTS MAY NEED TO BE RAISED. THE

CURRENT TIMING DOES BRING SNOW IN DURING THE AFTERNOON AND

CONTINUES THROUGH THE EVENING WHICH MAY HAVE A NEGATIVE IMPACT ON

THE TUESDAY EVENING COMMUTE.

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Stebo

Stebo

Posted
Posted

NAM has certainly shifted the track of the H5 low south a bit. Doesn't maintain the primary low track through the GLs either. Looks like it's trended towards the newer GFS/EURO depictions.

Yeah this run was a slight downward trend but probably closer to reality.

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dmc76

dmc76

Posted
Posted

If that qpf verifies you will get more than 3". This is not going to be a 10-1 ratio snow, even if flake size is an issue it will be at least 12-1. If dendrites are great it will be much higher.

On Average temps will be in the low 20's it could be higher then 12 to 1...Im thinking around 15 to 1. This is event where north 59 will be figting that North winds thats why I think there could be banding south of me somewhere between 94 and 59 where the biggest accumulation will occur. Another thing storm starts mid to late PM...which will also raise the ratios

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snowstormcanuck

snowstormcanuck

Posted
Posted

On Average temps will be in the low 20's it could be higher then 12 to 1...Im thinking around 15 to 1. This is event where north 59 will be figting that North winds thats why I think there could be banding south of me somewhere between 94 and 59 where the biggest accumulation will occur. Another thing storm starts mid to late PM...which will also raise the ratios

Temps do affect snow liquid ratios, but a bigger factor is where the best omega is with respect to the DGZ (dendritic growth zone). BUFKIT has some cool features that allows you to determine that.

And could you explain the bolded part.

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Organizing Low

Organizing Low

Posted
Posted

NAM has certainly shifted the track of the H5 low south a bit. Doesn't maintain the primary low track through the GLs either. Looks like it's trended towards the newer GFS/EURO depictions.

yes overnight modeling is not headed in the right direction, for southern ontario.....hopefully you can still get some accumlation out of this one though.

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dmc76

dmc76

Posted
Posted

Temps do affect snow liquid ratios, but a bigger factor is where the best omega is with respect to the DGZ (dendritic growth zone). BUFKIT has some cool features that allows you to determine that.

And could you explain the bolded part.

According to DTX storm arrives in or around PM rush hour...so if it snows at night it helps out snow ratios more if the storm would have starting after dawn....

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Powerball

Powerball

Posted
Posted

Temps do affect snow liquid ratios, but a bigger factor is where the best omega is with respect to the DGZ (dendritic growth zone). BUFKIT has some cool features that allows you to determine that.

And could you explain the bolded part.

Yeah, I don't get it either.

I thought the mid-late afternoon was the worst period for high snow ratios given peak heating.

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baroclinic_instability

baroclinic_instability

Posted
Posted

Yeah, I don't get it either.

I thought the mid-late afternoon was the worst period for high snow ratios given peak heating.

Not true. This does become a concern in Spring where insolation (incoming solar radiation) can keep ground temps warm and snow melts immediately. In the dead of winter, time of day does not effect snow ratios in any way, nor do temperatures at the surface.

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Powerball

Powerball

Posted
Posted

The sun angle in early January isn't going to have more than a negligible effect on snow ratios. I wouldn't worry about that.

I suppose it's negligible based on a number of factors (snowfall duration, snowfall intensity, snowflake size).

Even during the lake effect event Friday we struggled for the first 1/2 hour on the surface with acumulations.

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baroclinic_instability

baroclinic_instability

Posted
Posted

I posted this in the first section last night, I will post it again for those asking about ratios. This was about the DGZ, but it can refer to crystal growth at any zone. 2M temps alone don't give an accurate representation of snow ratios.

"One minor thing to note for everyone here. When assessing a DGZ, one must not simply assess if the sounding is saturated through the optimal thermal regime, but one must assess vertical ascent through that layer as well as moisture levels to fully come to a conclusion. Crystal growth is a pretty challenging thing to truly forecast and is quite fickle. Even dendrite growth alone can happen but be sub-optimal depending on a number of factors. "

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snowstormcanuck

snowstormcanuck

Posted
Posted

I suppose it's negligible based on a number of factors (snowfall duration, snowfall intensity, snowflake size).

Even during the lake effect event Friday we struggled for the first 1/2 hour on the surface with acumulations.

With LES because it's low topped convection, the sun has an easier time emitting heat through the clouds. That's not the case with a synoptic storm. And even in the case of LES, unless temps were marginal, and we're talking about dark surfaces, I can't believe the sun had any substantial effect on the amount of accumulation.

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toronto blizzard

toronto blizzard

Posted
Posted

With LES because it's low topped convection, the sun has an easier time emitting heat through the clouds. That's not the case with a synoptic storm. And even in the case of LES, unless temps were marginal, and we're talking about dark surfaces, I can't believe the sun had any substantial effect on the amount of accumulation.

Some of the SREF members show LES around the west end of lake ontario. Also the 00z GGEM seemed to show some lake effect. Your take?

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